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Journal : Indonesian Journal of Forestry Research

RELATIONSHIPS BETWEEN TOTAL TREE HEIGHT AND DIAMETER AT BREAST HEIGHT FOR TROPICAL PEAT SWAMP FOREST TREE SPECIES IN ROKAN HILIR DISTRICT, RIAU PROVINCE Nugroho, Nunung Puji
Indonesian Journal of Forestry Research Vol. 1 No. 2 (2014): Indonesian Journal of Forestry Research
Publisher : Association of Indonesian Forestry and Environment Researchers and Technicians

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.59465/ijfr.2014.1.2.89-107

Abstract

Reliable information on total tree height (H) is fundamental in forest resource management and forest ecological studies, including in forest biomass assessment. Adding an H variable can improve the performance of the biomass allometric equations by reducing the average deviation significantly. However, measuring H is relatively complex, less accurate, time consuming, and expensive. Thus, H is only measured for sampled trees within the plots, whilst diameter at breast height (DBH) is commonly measured for each tree during the forest inventory. The missing H information is usually estimated based on a stand-specific allometric relationship between H and DBH (H-D model) constructed from sampled trees. Despite extensive studies on H-D model for boreal forests and for single-species/plantation forests, few studies have focused on tropical forests. Furthermore, relationships for peat swamp forest tree species, and especially those in Indonesia, have not been widely published. Thus, the objective of this study was to develop site-specific H-D models for tropical peat swamp forests using linearized and non-linear regression functions. The results indicated that the non-linear models outperformed the linearized models based on the statistical parameters and the biological criteria. The modified logistic function (Model 7) is recommended for estimating H in the study area as it has comparable model performances to the exponential function (Model 6) and passed the point diameter-height of (0, 1.3). However, all five non-linear models performed equally well and the differences between them were trivial.
DEVELOPING SITE-SPECIFIC ALLOMETRIC EQUATIONS FOR ABOVE-GROUND BIOMASS ESTIMATION IN PEAT SWAMP FORESTS OF ROKAN HILIR DISTRICT, RIAU PROVINCE, INDONESIA Nugroho, Nunung Puji
Indonesian Journal of Forestry Research Vol. 1 No. 1 (2014): Indonesian Journal of Forestry Research
Publisher : Association of Indonesian Forestry and Environment Researchers and Technicians

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.59465/ijfr.2014.1.1.47-65

Abstract

In forest biomass assessment studies, the selection or development of reliable allometric biomass equations is an essential step which determines largely the accuracy of the resulted biomass estimates. Unfortunately, only few studies on allometric biomass equations have been conducted for peat swamp forests and the results are usually not publicly accessible or well documented. Thus, the objective of this study was to develop site-specific allometric equations for above-ground biomass (AGB) estimations in tropical peat swamp forests in Indonesia. These equations were developed based on 51 destructively sampled trees. The results indicated that the developed site-specific allometric equations have coefficient of determination (R2) greater than 95%. The R2 values ranged from 97.0% to 98.7%, where the lowest R2 value resulted from the simplest model which used only DBH as a predictor. Model 5, which used DBH, H and ρ as predictive variables, provided best performance when estimating the AGB of the study area. Hence, as long as reliable data are available as input, Model 5 is recommended. The accuracy and applicability of the allometric equations for peat swamp forests could be improved further by adding more sampled trees from different tree species and/or with a wider DBH range. Considering the importance of wood density in the estimation of the AGB and the lack of this information for peat swamp forest tree species, research should be dedicated to analysing the wood density of the dominant tree species comprising the majority of the AGB density in the study area.